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AQA Physics PHYA5 - Thursday 18th June 2015 [Exam Discussion Thread]

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They can definitely ask us about the first bit because that's just the basics of black body radiation (Wien's law), and I'd say the second bit isn't a huge jump (our teacher talked about it a fair bit) so it could come up I expect.
Yeah, you just have the colours in the table for OBAFGKM - basically anything except green can turn up!

Thank you! :smile:

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Reply 1081

CD223

Original post by Normal.Person

GUYS!
Just an fyi for everyone doing this exam, got some info that I thought might help everyone:
No need to thank me.

Spoiler

That is not a way to make friends on this site :wink:

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Reply 1082

Absent Agent

Original post by Normal.Person

GUYS!
Just an fyi for everyone doing this exam, got some info that I thought might help everyone:
No need to thank me.

Spoiler

Lol, that's physics unit 5 nth birthday :smile:

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Reply 1083

Normal.Person

Original post by CD223

That is not a way to make friends on this site :wink:

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LOOL, banter is good. Especially during exam time :P

Reply 1084

CD223

Original post by Normal.Person

LOOL, banter is good. Especially during exam time :P

Times of high stress call for times of high level banter.

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Reply 1085

runningoutoftime

The moment where thermal physics makes you break down in tears!!

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Reply 1086

Absent Agent

Original post by runningoutoftime

The moment where thermal physics makes you break down in tears!!

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I believe the moment hasn't come yet ;(

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Reply 1087

CD223

Original post by runningoutoftime

The moment where thermal physics makes you break down in tears!!

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I think it will be the six marker this year :/

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Reply 1088

runningoutoftime

Original post by CD223

I think it will be the six marker this year :/

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What do you think it could be one? Kinetic theory?

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Reply 1089

AR_95

Original post by runningoutoftime

What do you think it could be one? Kinetic theory?

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Has ideal gas come up as a 6 marker before? I just really hate the kinetic theory :frown:

Reply 1090

CD223

Original post by runningoutoftime

What do you think it could be one? Kinetic theory?

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Original post by AR_95

Has ideal gas come up as a 6 marker before? I just really hate the kinetic theory :frown:

Proof of the equation or a SHC/SLH experiment :smile:

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Reply 1091

AR_95

Original post by CD223

Proof of the equation or a SHC/SLH experiment :smile:

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Proof of which equation?

Reply 1092

runningoutoftime

Original post by CD223

Proof of the equation or a SHC/SLH experiment :smile:

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i thought we didnt have to dervive the equation?

Reply 1093

AR_95

Things I hope come up :

Standard "calculate ze age of ze isotope"

How a nuclear reactor works questions

Standard Q=MCT question

Also out of the 4 topics in PH5, which one do you find the easiest when solving the numerical questions? For me it's all the gases parts

Reply 1094

imyimy

hello, stuck on this question, any ideas?

Question 13 on here

http://www.wolgarston.staffs.sch.uk/wp-content/uploads/2015/01/Y13-GCE-Physics-PHYA5-spring-1-201415-20.pdf

Some liquids in open bottles deteriorate on exposure to air. The diagram below shows one device used to reduce this deterioration. It consists of a rubber valve that is inserted into the neck of the bottle together with a pump that is used to remove some of the air in the bottle through this rubber valve. On an up-stroke of the pump, air enters the pump chamber from the bottle. On the down-stroke, the rubber valve closes and the air in the chamber is expelled to the atmosphere through another valve (not shown) in the handle.

a.) There is 3.5 × 10–4 m3 of air space in the bottle and the volume of the pump chamberchanges from zero at the beginning of the up-stroke to 6.5 × 10–5 m3 at the end of the up-stroke. The initial pressure of the air in the bottle is that of the atmosphere with a value of99 kPa.

Assuming the process is at constant temperature, calculate the pressure in the bottle afterone up-stroke of the pump.

b.) Calculate the number of molecules of air originally in the air space in the bottle at atemperature of 18 °C.

c.) Explain how the kinetic theory of an ideal gas predicts the existence of a gas pressureinside the bottle. Go on to explain why this pressure decreases when some of the air isremoved from the bottle.

answers in spoiler

Spoiler

thank you in advance

Reply 1095

a.a.k

Original post by imyimy

(where did 4.15 come from???

Before there was only volumes inside bottle after theres is volme of both bottle and the pump(or valve etc)
So you add both volumes.

3.5 x 0^-4 +6.5x10^-5 = 4.15 x 10^-4

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(edited 8 years ago)

Reply 1096

a.a.k

Original post by imyimy

used pV=Nkt and got 8.62x10^21 +21 rather than -21???)

Use pV=nRT

Small n is number of moles
Big N is number particles

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Reply 1097

imyimy

Original post by a.a.k

Use pV=nRT

Small n is number of moles
Big N is number particles

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thanks

but the question asks for molecules not moles

Reply 1098

a.a.k

Original post by imyimy

thanks

but the question asks for molecules not moles

Oh sorry my bad

Yeah u find the number if moles then divide by avagadro constant to get number of particles or in this case number of molecules

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